The present invention relates to a sliding member comprising an overlay layer made of Bi (bismuth) or a Bi alloy.
In an internal combustion engine used in an automobile etc. are used sliding bearings in each of which a Cu-based or Al-based bearing alloy is used and on the surface of each of which an overlay layer is usually provided to enhance the conformability thereof. Hitherto, as the material of the overlay layer, a Pb alloy has been used which is soft in hardness, or a Sn alloy has been used in some cases.
Since Pb is a substance causing environmental pollution, it is desired to cease the use thereof, and various researches have been performed for ceasing the use of Pb. For example, in JP-A-2001-20955, it is disclosed to use Bi instead of the use of Pb.
However, since Bi is brittle and is inferior regarding anti-seizure property, Bi is not suitable as the material of the overlay layer which is required to have good fatigue resistance and good conformability. Thus, in a case of using Bi as the material of the overlay layer, it is necessary to improve such properties of Bi as to be brittle and inferior in the anti-seizure property, so that the overlay layer made of a material containing Bi may be practically usable.